Estimation of thermoelectric and mechanical performances of segmented thermoelectric generators under optimal operating conditions

The conversion efficiency is the most important indicator describing the thermoelectric performance of thermoelectric (TE) devices. Under large operating temperature difference, the efficiency can be enhanced by the fabrication of segmented thermoelements structure. For running safety, the thermomechanical behavior of TE devices must be considered. In this paper, a 3D finite element model is established to estimate the TE and mechanical performance of the segmented thermoelectric generator (STEG) under optimal operating conditions. The effects of the segment lengths on the TE conversion efficiency and the maximum stress level of TE materials are examined at a given operating temperature. And for different operating temperatures, the maximum conversion efficiency and maximum stress level of TE materials are also investigated, individually. By the mechanical strength evaluation and mechanical reliability analysis, the TE behaviors of STEG are verified. The results indicate that, for a given operating temperature, some segmented cases do not satisfy the strength requirements, and the theoretical maximum efficiency does not equal to the actual optimal one; for different operating temperatures, the STEG cannot always achieve the maximum design value of conversion efficiency. These findings will have some significant positive impact on the optimal design and practical application of the STEG.